The present invention relates to a device for equalizing multiphase and/or multiamplitude modulated data signals by means of a decider and an equalizing filter, in which a difference forming member feeds a representation of the difference between the demodulated decider output and input signals to the equalizer filter as a control value for the adaptive setting of the equalizer coefficients.
Such a device is disclosed in the paper entitled "Datenubertragung mit 4,8 kBit/sec im Fernsprechnetz: Entwurf und Realisierung eines Modems nach den CCITT Empfehlungen V. 27 bis /ter" [Data Transmition operating at 4.8 kBit/sec in a telephone network: Design and realization of a modem according to CCITT Recommendations V. 27 bis /ter] by Gockler, Hofmeister and Till, published by Wissenschaftliche Berichte [Scientific Reports] AEG-TELEFUNKEN, Vol. 51 (1978), No. 4/5, pages 231-245.
The drawback in such adaptive equalizing devices is that due to the limited word length, there may be an overrun of the coefficients even when there are no extreme channel distortions.